1. Field of the Invention
The present invention relates generally to heat exchangers, such as condensers for automotive vehicles. More particularly, the present invention relates to a condenser and a method for making the condenser wherein the internal diameter of the condenser tubing is deformed to a predetermined limit during the manufacture of the condenser.
2. Disclosure Information
Fin and tube type heat exchangers are commonly used in vehicle, industrial and residential environments for heating and Cooling purposes. Typically, these heat exchangers utilize a plurality of hairpin-shaped tubes to form a condenser or the like wherein the fluid passes through the plurality of tubes. The number of tubes depends upon the thermal capacity requirements of the fin and tube heat exchanger. Interleaved between the plurality of tubes are a plurality of stacked fin members which aid in dissipating the heat from the condenser as is well known in the art. A manifold interconnects the tubes so that fluid can flow therethrough.
To ensure good heat transfer between the tubes and the fins, there must be significant contact between the outer diameter of the tubes and the fins. In order to accomplish this, it is well known in the art to insert a bullet-like tool or expander plug into the heat transfer tube and displace the tool axially with respect to the tube to effect radial expansion of the tube into gripping engagement with the surrounding fins. It is also well known that one method to increase the thermal transfer coefficient of the tubing is to increase its internal surface area by providing surface irregularities therein. Typically, these irregularities are in the forms of grooves which, as shown in U.S. Pat. No. 3,517,536, are formed by inserting a bullet-like tool having cutting edges thereon which form grooves along the inner diameter of tube. Typically, the tool is rotated along the axial length of the tubing to form spiral grooves therein. However, because of tool wear during repeated expanding operations, the uniformity of the spiral grooves often changes and the efficiency of the heat exchanger decreases. It would, therefore, be advantageous to provide a method for making a heat exchanger wherein the internal surface irregularities of the tubing remains more uniform during the manufacturing process.
In most known manufacturing operations, the internal surface of the tubing is smooth prior to the insertion of the expander plug and the forming of the helical grooves therein. Prior to the present invention, it has not been known to expand the tubing wherein the surface irregularities are formed integral with the tube prior to the expansion process, and where the height of the surface irregularities are maintained to a specific height after expansion of the tubing to retain heat transfer characteristics.